Transmitter Design and Synchronization Concepts for DaViD Display Camera Communication

Visible Light Communication is a promising technology for data transmission, which has become more and more relevant in recent years. Other than the common approach of modulated LED lighting, display-camera communication has become an attractive novel take on the concept. As outlined in earlier papers, the DaViD (Data Transmission Using Video Displays) system provides a modulation concept allowing for a data overlay onto video content which is nearly invisible to the viewer, i.e. causing hardly any perceptible degradation in video quality. This is achieved by differentially modulating the chrominance information of the underlying video frames with low amplitudes. The resulting color differences within the recorded images can be interpreted by the receiver, allowing for reconstruction of the transmitted data. In this paper, we introduce further system details and improvements to the DaViD concept. In addition to traditional transmission systems, on the display-camera link, the receiver has to be not only temporally but also spatially synchronized to the transmitter. We address the spatial synchronization problem by utilizing localization patterns for detecting the modulation area and a separate optimization on columns and rows for data resampling. Using a slight temporal oversampling, clean data frames can be reconstructed on the receiver side. Based on our modulation and coding concept, we achieve a data rate up to 34.56 Mbit/s in our current demonstration setup with hardly any visible degradation in video quality.